1.\" $NetBSD: gettimeofday.2,v 1.22 2003/08/07 16:43:59 agc Exp $ 2.\" 3.\" Copyright (c) 1980, 1991, 1993 4.\" The Regents of the University of California. All rights reserved. 5.\" 6.\" Redistribution and use in source and binary forms, with or without 7.\" modification, are permitted provided that the following conditions 8.\" are met: 9.\" 1. Redistributions of source code must retain the above copyright 10.\" notice, this list of conditions and the following disclaimer. 11.\" 2. Redistributions in binary form must reproduce the above copyright 12.\" notice, this list of conditions and the following disclaimer in the 13.\" documentation and/or other materials provided with the distribution. 14.\" 3. Neither the name of the University nor the names of its contributors 15.\" may be used to endorse or promote products derived from this software 16.\" without specific prior written permission. 17.\" 18.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 19.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 20.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 21.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 22.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 23.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 24.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 25.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 26.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 27.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 28.\" SUCH DAMAGE. 29.\" 30.\" @(#)gettimeofday.2 8.2 (Berkeley) 5/26/95 31.\" 32.Dd May 26, 1995 33.Dt GETTIMEOFDAY 2 34.Os 35.Sh NAME 36.Nm gettimeofday , 37.Nm settimeofday 38.Nd get/set date and time 39.Sh LIBRARY 40.Lb libc 41.Sh SYNOPSIS 42.In sys/time.h 43.Ft int 44.Fn gettimeofday "struct timeval *tp" "struct timezone *tzp" 45.Ft int 46.Fn settimeofday "const struct timeval *tp" "const struct timezone *tzp" 47.Sh DESCRIPTION 48.Bf -symbolic 49Note: time zone information is no longer provided by this interface. 50See 51.Xr localtime 3 52for information on how to retrieve it. 53.Ef 54.Pp 55The system's notion of the current UTC time is obtained with the 56.Fn gettimeofday 57call, and set with the 58.Fn settimeofday 59call. 60The time is expressed in seconds and microseconds 61since midnight (0 hour), January 1, 1970. 62The resolution of the system clock is hardware dependent, 63and the time may be updated continuously or in ``ticks.'' 64If 65.Fa tp 66is NULL, the time will not be returned or set. 67.Pp 68The structures pointed to by 69.Fa tp 70and 71.Fa tzp 72are defined in 73.Ao Pa sys/time.h Ac 74as: 75.Pp 76.Bd -literal 77struct timeval { 78 long tv_sec; /* seconds since Jan. 1, 1970 */ 79 long tv_usec; /* and microseconds */ 80}; 81 82struct timezone { 83 int tz_minuteswest; /* of Greenwich */ 84 int tz_dsttime; /* type of dst correction to apply */ 85}; 86.Ed 87.Pp 88The 89.Fa timezone 90structure is provided only for source compatibility. 91It is ignored by 92.Fn settimeofday , 93and 94.Fn gettimeofday 95will always return zeroes. 96.Pp 97If the calling user is not the super-user, then the 98.Fn settimeofday 99function in the standard C library will try to use the 100.Xr clockctl 4 101device if present, thus making possible for non privileged users to 102set the system time. 103If 104.Xr clockctl 4 105is not present or not accessible, then 106.Fn settimeofday 107reverts to the 108.Fn settimeofday 109system call, which is restricted to the super user. 110.\" XXX uncomment when/if this is put into place! 111.\" If the system is running in secure mode (see 112.\" .Xr init 8 ), 113.\" the time may only be advanced. 114.\" This limitation is imposed to prevent a malicious super user 115.\" from setting arbitrary time stamps on files. 116.\" The system time can still be adjusted backwards using the 117.\" .Xr adjtime 2 118.\" system call even when the system is secure. 119.Sh RETURN VALUES 120A 0 return value indicates that the call succeeded. 121A -1 return value indicates an error occurred, and in this 122case an error code is stored into the global variable 123.Va errno . 124.Sh ERRORS 125The following error codes may be set in 126.Va errno : 127.Bl -tag -width Er 128.It Bq Er EFAULT 129An argument address referenced invalid memory. 130.It Bq Er EPERM 131A user other than the super user attempted to set the time, or the specified 132time was less than the current time, which was not permitted at the current 133security level. 134.El 135.Sh SEE ALSO 136.Xr date 1 , 137.Xr adjtime 2 , 138.Xr ctime 3 , 139.Xr localtime 3 , 140.Xr clockctl 4 , 141.Xr timed 8 142.Sh HISTORY 143The 144.Fn gettimeofday 145function call appeared in 146.Bx 4.2 . 147The 148.Fa tzp 149argument was deprecated in 150.Bx 4.4 151(and many other systems). 152